Multi-stand rolling mill for rod-shaped bodies comprising three motorized-rollers stands

ABSTRACT

The present invention relates to a multi-stand rolling mill (1) for tubular bodies. The rolling mill comprises a first section (10) for rolling on mandrel defined by a first plurality of rolling stands (15′, 15, 15″) arranged in sequence along a rolling axis (100). According to the invention, the rolling mill also comprises a second rolling section without mandrel, arranged down-stream of said first section, which comprises a second plurality of stands (25′, 25, 26, 27, 26′, 27′) arranged in sequence along said rolling axis (100). Each stand (25′, 25, 26, 27, 26′, 27′) of said second section (20) comprises three rollers having rotation axes which are arranged at 120° from one another. The rotation axes for each stand (25′, 25, 26, 27, 26′, 27′) are rotated by 180° with respect to corresponding rotation axes of an adjacent stand. According to the invention, at least one stand of said second section (20) comprises a motorized roller having a vertical rotation axis.

CROSS REFERENCE TO RELATED APPLICATION(S)

The present application claims priority to PCT International ApplicationNo. PCT/IB2016/056328 filed on Oct. 21, 2016, which application claimspriority to Italian Patent Application No. 102015000064939 filed Oct.23, 2015, the entirety of the disclosures of which are expresslyincorporated herein by reference.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable.

FIELD OF THE INVENTION

The present invention falls within the scope of achieving rollingsystems of tubular bodies. Namely, the invention relates to amulti-stand rolling mill comprising stands having three motorizedrollers. In particular, the rolling mill is configured to perform arolling on mandrel and a successive rolling without mandrel of thetubular bodies along a same line.

BACKGROUND ART

Plants are known for the production of hollow bodies (or tubular bodies)such as e.g. seamless tubes. In particular, such a production includesthree basic deformation steps, the first of which being identified inthe longitudinal drilling of the bodies. The bodies then undergo a firstrolling on mandrel, along a first line, in order to define the thicknessof the tube. At the end of the first rolling and following theextraction of the mandrel, the tubes are processed in a heating furnacein which they are kept at a predetermined temperature before undergoing,on a second line, a further rolling without mandrel, that is in theabsence of a mandrel, aimed to calibrate the diameter of the tubesthemselves.

An example of this production process is described and disclosed inPatent Application EP2008732. In particular, in this known solution, therolling on mandrel is performed through two-rollers rolling stands,while the rolling without mandrel is performed through three-rollersstands. A heating furnace is provided between the two rolling lines.Patent Application EP2878390 instead describes a line in which therolling on mandrel occurs through three-rollers stands.

Patent applications PCT/EP2013/071021 and PCT/EP2009/056201 describe andshow other rolling mills in which the rolling without mandrel occursthrough three-rollers stands. In particular, the stands in ApplicationPCT/EP2009/056201 have rollers having a position which is adjustablewith respect to the rolling axis.

The calibration rolling typically is performed through threemotorized-rollers rolling stands, each rotating about a rotation axiswhich is inclined by 120° with respect to the axes of the other rollers.Typically, one of the rollers has a horizontal rotation axis actuated bya horizontal axis drive shaft. The other two rollers instead areactuated by corresponding drive shafts, one of which is operativelyinstalled below the support surface of the rolling stands. Examples ofsuch rolling stands are described e.g. in Applications US 2001/0027674,DE 100 15285 and U.S. Pat. No. 7,424,816.

Rolling stands with three rollers are also known in the art, typicallyone of which rollers having a horizontal rotation axis actuated by ahorizontal axis drive shaft, while the other two rollers instead areactuated by means of inner conical gears which connect the horizontalrotation axis of the first roller with each of the two inclined rotationaxes of the other two rollers. A solution of this type is described inApplication EP 1449597, for example. The rolling plants described abovehave various drawbacks, the first one of which being the overalldimensions which are decisively affected by the presence of the heatingfurnace. In general, the presence of the heating furnace is critical forvarious other reasons, among which the complicated management of tubeaccumulations, the problem of excessive decarburization and/or oxidationin the event of a prolonged stop inside the furnace, the loss of weightgenerated by the formation of scale inside the furnace. Overall, allthese aspects affect the manufacturing/management costs of the plant andaccordingly the production costs. Other drawbacks of the systems,described above are associated with the technical solutions currentlyused for the calibration rolling. In particular, it has been shown thatthe operation for replacing the stands, also referred to asstand-replacement, is particularly complex due to the configuration ofthe three-rollers stands typically used. Indeed, the use of a horizontalaxis roller motorized by means of a horizontal drive shaft does not makethe replacement of the stand of the rolling line very convenient. At thesame time, the arrangement of the other rollers and of the relatedactuation drive shafts requires a complex support structure and just ascomplex a foundation system below the support surface of the stands,which is required to accommodate the motorization means of one of thedrive shafts in the case of individually controlled rollers.

The considerations above reveal the need to provide a new rolling systemwhich allows the drawbacks mentioned above to be overcome.

SUMMARY

The present invention relates to a rolling mill for tubular bodiescomprising a first section for rolling on mandrel defined by a firstplurality of rolling stands arranged in sequence along a rolling axis.The rolling mill according to the invention further comprises a secondsection for the extraction of the mandrel and the calibration of thetubular bodies. Such second section is arranged downstream of the firstsection whereby the tubular bodies exiting from said first section (10)directly enter said second section (20). Such a second section comprisesa second plurality of rolling stands without mandrel, arranged insequence along said rolling axis. Each stand of the second sectioncomprises three rollers having rotation axes which are arranged at 120°with respect to one another and wherein the rotation axes for each standare rotated by 180° with respect to corresponding rotation axes of anadjacent stand, said position of said rotation axes being assessed withrespect to a vertical reference direction. Moreover, according to theinvention, at least one stand of the second section comprises amotorized roller having a vertical rotation axis.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and advantages of the present invention will become apparentfrom the detailed description provided below of an embodiment thereofand from the accompanying drawings merely given by way of a non-limitingexample, in which:

FIGS. 1 to 4 are schematizations related to possible embodiments of arolling mill according to the invention, comprising a first rollingsection and a second rolling section;

FIG. 5 is a side view of the second section of the rolling millschematized in FIG. 1;

FIG. 6 is a side view of the second section of the rolling millschematized in FIG. 2;

FIG. 7 is a plan view of the rolling mill in FIG. 5;

FIG. 8 is a view according to the sectional plane VIII-VIII in FIG. 5;

FIG. 9 is a perspective view of a fixed rollers stand of a secondsection of a rolling mill according to the present invention;

FIG. 10 is a view according to the sectional plane X-X in FIG. 9;

FIG. 11 is a perspective view of a group of adjustable rollers stands ofa second section of a rolling mill according to the present invention;

FIG. 12 is a first sectional view according to plane XII-XII in FIG. 11;

FIG. 13 is a second sectional view according to plane XIII-XIII in FIG.11;

FIG. 14 is a plan view of the group of stands in FIG. 11;

FIG. 15 is a sectional view according to line XV-XV in FIG. 13;

FIG. 16 is a view according to the sectional plane XVI-XVI in FIG. 5;

FIG. 17 is a view according to the sectional plane XVII-XVII in FIG. 7;

FIG. 18 is a sectional view according to the plane XVIII-XVIII in FIG.7.

The same numbers and the same reference letters in the figures identifythe same elements or components.

DETAILED DESCRIPTION

With reference to the figures mentioned, the present invention relatesto a multi-stand rolling mill 1 for hollow bodies (hereinafter alsoindicated as tubular bodies). The rolling mill 1 according to theinvention comprises a first rolling section 10 on tool, or on mandrel,previously inserted inside the hollow body according to a principlewhich is in itself known. The first section 10 serves the function ofdefining the thickness of the hollow body and comprises a firstplurality of rolling stands 15′, 15, 15″ arranged in sequence accordingto a rolling axis 100 (or rolling direction 100). In particular, thefirst section 10 comprises at least one inlet stand 15′ arranged on aninlet side 10′ and at least one outlet stand 15″ arranged on an outletside 10″ of the first section. Therefore, a feeding direction 200 of thehollow body is defined along the rolling axis 100 so that the inletstand 15′ is the first which intervenes on the hollow body, while theoutlet stand 15″ is the last which intervenes by completing thedefinition of the thickness.

The rolling mill 1 according to the invention further comprises a secondrolling section 20 without mandrel, arranged downstream of the firstsection 10 with respect to said feeding direction 200. Such a secondsection 20 serves the function of performing the extraction of themandrel from the hollow body and of calibrating the diameter of thehollow body. The term “without mandrel” means rolling which is performedin the absence of a mandrel, i.e. following the extraction thereof.According to the invention, the second section 20 defines a rolling axiswhich coincides with the rolling direction 100 defined by the firstsection 10. Therefore, the rolling on mandrel and the rolling withoutmandrel are performed on the same line (rolling direction 100). Inessence, the hollow bodies exiting from the first section 10 directlyenter the second section 20 for the extraction of the mandrel from thehollow body and for the calibration of the diameter. This solutionadvantageously avoids the installation of an intermediate heatingfurnace, thus obtaining a reduction in the length of the system by atleast 70 meters (length of a traditional heating furnace and a outletroller way before the inlet of the intermediate furnace with a possibleintermediate cooling surface) with respect to traditional solutions.Moreover, all the above-described problems associated with installingand managing the furnace itself (decarburization and/or oxidation,formation of scale) are eliminated. Advantageously, the productionprocess is in fact limited to two deformation steps only: drilling androlling (thickness/calibration). The first section 10 and the secondsection 20 in fact form a single in line mill which integrates thicknessrolling and diameter calibration. Therefore, a drastic simplification isobtained of the tracking of the hollow bodies, since there are nointermediate accumulations caused by the intermediate furnace.

According to the present invention, the second section 20 comprises asecond plurality of rolling stands 25, 26, 27, 26′ 27′ arranged insequence along said rolling axis 100 starting from an inlet side 20′.Thus, an inlet stand 25′ is identified, which intervenes on the hollowbody coming from the first section 10. Moreover, an outlet stand isidentified, which is the last stand crossed by the hollow body beforeleaving the second section 20. Said stands 25′, 25, 26, 27, 26′, 27′ arearranged on a substantially horizontal support surface 300.

Each stand 25, 26, 27, 26′, 27′ of the second section 20 comprises threerolling rollers having rotation axes which are arranged at 120° from oneanother. Moreover, the rotation axes of the rollers for each stand 25,26, 27, 26′, 27′ of the second section 20 are rotated by 180° withrespect to the rotation axes of an adjacent stand. More in details, theposition of the axes of any one stand with respect to those of anadjacent stand, is assessed with respect to a vertical direction 150which is orthogonal to the support surface 300. In this regard, FIGS. 1a and 1 b are schematized for the purposes of showing such anarrangement. Specifically, FIG. 1a schematizes the arrangement of theaxes of rollers A, B, C in a stand taken as a reference, while FIG. 1bschematizes the arrangement of rollers A′, B′, C′ of an adjacent stand.The term “adjacent” means a stand which may be upstream or downstreamwith respect to the stand taken as a reference with respect to thefeeding direction 200.

According to the present invention, at least one rolling stand of thesecond section 20 comprises a motorized roller having a verticalrotation axis. Preferably, such a roller is motorized through a driveshaft, which also has a vertical axis. As specified better below, theuse of one or more stands with a vertical axis motorized rolleradvantageously simplifies the replacement of the stands of the secondsection 20, thus drastically decreasing the times related to thisoperation.

According to another aspect of the present invention, the second section20 of rolling mill 1 comprises at least one fixed rollers stand, thisexpression meaning a stand in which the position of the rollers (i.e. oftheir rotation axes) is not adjustable/modifiable with respect to therolling axis 100. Said at least one fixed rollers stand comprisesmechanical transmission means configured to transmit the motion from oneof said rollers, preferably from the vertical axis motorized roller, tothe other two rollers of the stand. FIGS. 9 and 10 commented on belowshow a possible embodiment of a fixed rollers stand of a rolling millaccording to the invention.

According to a preferred embodiment, the rolling mill 1 according to theinvention comprises a first series of fixed rollers stands 25′, 25(hereinafter also indicated with the expression first stands 25′ 25)arranged in sequence along said rolling axis 100 starting from the inletside 20′ of the second section 20. Therefore, the inlet stand 25′ is afixed rollers stand.

According to a further aspect, also the rolling stands 15′, 15, 15″ ofthe first section 10 of the rolling mill 1 have three rolling rollershaving rotation axes which are arranged at 120° from one another.According to the invention, the rotation axes of the inlet stand 25′ ofthe second section 20 are rotated by 180° with respect to the rotationaxes of the rollers of the outlet stand 15″ of the first section 10. Theposition of the axes is always assessed with respect to the verticalreference direction 150. In essence, the position of the rollers of theoutlet stand 15″ of the first section 10 with respect to the rollers ofthe inlet stand 25′ of the second section 20 follows what is shown inthe schematizations in FIGS. 1a and 1b . Through this contrivance, therollers of the rolling stands 15′, 15, 15″ of the first section 10advantageously are aligned with the rollers of the rolling stands 25′,25, 26, 27, 26′, 27′ of the second section 20. Thereby, the thicknesstolerances may be improved to the benefit of the improved quality of thefinal product.

Preferably, each fixed rollers stand 25′, 25 comprises a vertical axismotorized roller 31 and mechanical transmission means configured totransmit the motion from such a motorized roller to the other tworollers of the stand. Preferably, said vertical axis roller is motorizedthrough a vertical axis drive shaft for each fixed rollers stand 25′,25. This solution is also advantageous because it allows the foundationsof the second section 20 to be simplified, as described below in thecomments on FIG. 17.

The second section 20 of the rolling mill 1 preferably comprises atleast one adjustable rollers stand operatively positioned downstream ofthe fixed rollers stand or stands 25′, 25. The expression “adjustablerollers stand” means a stand in which the distance of the rollers fromthe rolling axis 100 can be adjusted in order to vary the rollingconditions and implement a corresponding variation in diameter.Preferably, said at least one adjustable rollers stand also comprises avertical axis motorized roller.

According to a preferred embodiment shown in the drawings, the rollingmill 1 comprises a series of adjustable rollers stands 26, 27, 26′, 27′(or second stands 26, 27, 26′, 27′) arranged in sequence along therolling axis 100 downstream of the fixed stands 25′, 25, again withrespect to the feeding direction 200. Preferably, each of the secondstands 26, 27, 26′, 27′ comprises a first motorized vertical axis roller34, 34′.

According to a possible embodiment, the second section 20 also comprisesa dummy stand 28, this expression meaning a stand in which no thicknessreduction or deformation of the hollow body is performed, and in whichthe roller or rollers present have the only function of carrying andguiding the piece along the rolling direction 100. Such a dummy stand 28can be arranged for example, between a fixed rollers stand and anadjustable rollers stand or alternatively downstream of the adjustablerollers stand according to the plant engineering needs.

FIGS. 1 to 4 are diagrams related to the possible configuration of arolling mill 1 according to the present invention. In such diagrams, thefirst section 10 of the rolling mill 1 has the same configurationsubstantially defined by six rolling stands 15′, 15, 15″, each havingthree rollers as indicated above. The second section 20 overall definessixteen positions, each of which is destined to be occupied by a rollingstand (with fixed or adjustable rollers) or alternatively by a dummystand. In all diagrams, thirteen of the sixteen positions are configuredso as to accommodate a fixed rollers stand or alternatively a dummystand, while the last three positions are instead configured toaccommodate any type of stand (fixed rollers—adjustable rollers—dummystand).

In general, according to the present invention, the second section 20comprises a first stretch 21 defining a first series of lodgingpositions which may be occupied by a fixed stand 25′, 25 oralternatively by a dummy stand 28. The second section 20 also comprisesa second stretch 22 defining a second series of positions which may beoccupied by fixed stands, adjustable stands or dummy stands, wherein theadjustable stands also may be operatively connected in a group (60, 62).

According to the configuration shown in the diagram in FIG. 1, thesecond section 20 provides an equal number of fixed stands and more indetails provides fourteen fixed stands 25′, 25 arranged in sequencestarting from the inlet side 20′. The last two positions of the secondsection 20 are instead occupied by two adjustable rollers stands 26, 27.Preferably, the latter are connected to each other so as to form asingle group 60 of two adjustable rollers stands wherein at least onemotorized roller of one of the stands is operatively connected to aroller of the other stand. In the continuation of the present invention,such a group 60 is also indicated with the expression “even bi-stand 60”where “even” means that the two stands 26, 27 defining such a bi-standare used when the overall number of rolling stands is even.

In the diagram in FIG. 2, the second section 20 provides thirteen fixedstands 25′, 25 which occupy thirteen positions starting from the inletside 20′. Here, the first two positions of the second stretch 22(corresponding to the 14^(th) and 15^(th) positions of the secondsection 20) are occupied by another group 62 of adjustable stands 26′,27′ indicated hereinbelow with the expression “odd bi-stand 62”, wherethe term “odd” means that the two stands 26′ and 27′ which define such abi-stand are used when the overall number of rolling stands is odd. Thelast position of the second stretch 22 instead is occupied by a dummystand 28.

The even bi-stand 62 is conceptually and functionally similar to the oddbi-stand 60 because a motorized roller of one of the stands 26′ or 27′is operatively connected to a roller of the other stand. Indeed, thesame technical solutions in terms of motion definition and transmissionbetween the various parts preferably are provided for the bi-stands(even 60 and odd 62). It can be noted that both the bi-stands (even 60and odd 62) are actuated through actuation means, typically driveshafts, installed in predetermined positions along the second stretch 22of the second section 20. Therefore, in order to adapt to the actuationmeans installed at the positions the furthest left to the second stretch22, the odd bi-stand 62 has a configuration which in fact mirrors thatof the even bi-stand 60 with respect to a vertical plane containing therolling axis 100.

In the diagram in FIG. 3, there are instead provided eight fixed stands25′, 25 and six dummy stands 28 arranged in sequence downstream of thefixed stands 25′, 25. The last two positions (15^(th) and 16^(th)) ofthe second section 20 are occupied by the adjustable stands 26, 27 ofthe even bi-stand 60 similarly to the diagram in FIG. 1. Finally, in thediagram in FIG. 4, there are provided seven fixed stands 25′, 25downstream of which are arranged six dummy stands 28 in sequence. Thelast three positions instead are occupied by adjustable stands 26′, 27′of the odd bi-stand 62 and by a false stand 28 in a similar manner tothe diagram in FIG. 2.

In general, the configuration of the second section 20 in terms of thenumber and position of fixed stands 25′, 25 and of dummy stands 28 inthe first stretch 21 and in terms of the position of theadjustable/fixed/dummy stands in the second stretch 22, may varyaccording to process needs. In particular, the selection of the numberof stands used and the related arrangement in the rolling mill 1substantially depend on the reduction of the diameter which occurs inthe calibration step (second section 20). In this regard, it ispreferable to limit the number of diameters exiting from the firstsection 10 with respect to the number of diameters which may be obtainedat the outlet of the second section 20.

With reference to the sectional views in FIGS. 17 and 18 commented onbelow, it can be noted how the first stretch 21 of section 20 in factdoes not require any foundation below the support surface 300. Suchfoundations are always limited to the second stretch 22 which defines asignificantly lower number of positions than the number of positionsdefined by the first stretch 21. Indeed, according to the invention andcontrary to known solutions, the rolling without mandrel is mainlyperformed through fixed rollers stands.

With reference again to FIGS. 1 to 4, it can be noted that in therolling mill according to the invention, there is provided a first speedmeter 166 for measuring the feeding speed of the hollow body between thetwo sections 10, 20 of the rolling mill 1 in order to control the speedalong the second section 20. In this regard, the rolling mill 1 furthercomprises a second speed meter 167 operatively arranged at the outlet ofthe second section 20.

The rolling mill 1 further comprises a thickness gauge 178 also arrangedat the outlet of the second section 20. It can be noted that the in lineconfiguration of the rolling mill 1 according to the inventionadvantageously allows at least one of the thickness gauges required intraditional plants comprising two independent rolling lines, oneupstream of the heating furnace and the other downstream of the finalcalibrator, to be eliminated.

FIG. 5 and FIG. 6 are a side view of the second section 20 of a rollingmill 1 according to the diagram in FIG. 1 and according to the diagramin FIG. 2, respectively. In particular, the arrangement of the fixedstands 25′, 25 and of the even bi-stand 60 forming the second section 20can be noted in FIG. 5. The arrangement of the fixed stands 25′, 25, theodd bi-stand 62, the dummy stand 28 forming the second section 20instead can be noted in FIG. 6. It can be noted how the second stretch22 of the second section 20 allows the position of the adjustable standsto be varied using an even bi-stand 60 or alternatively an odd bi-stand62 according to operating needs.

FIG. 7 is a plan view of the second section 20 of the rolling mill shownin FIG. 5. FIG. 7 shows the even bi-stand 60 and the actuation means(drive shafts 30A, 30B, 30C) installed in the second stretch 22. It canbe noted that the bi-stand 60 is configured to interact with two driveshafts 30A, 30B (hereinafter indicated with “right-hand drive shaft 30A”and “left-hand drive shaft 30B”) arranged on opposite sides with respectto the rolling axis 100. The right-hand drive shaft is operativelyassociated with the second-last position of the second stretch 22, whilethe left-hand drive shaft is associated with the last position of thesame stretch. It can be noted from the comparison between FIGS. 5, 6 and7 how an odd bi-stand 62 (shown in FIG. 6), due to the differentposition which it should take on in the second stretch 22, is configuredto interact on the one side with the right-hand drive shaft 30A and onthe other with drive shaft 30C arranged on the same side as theleft-hand drive shaft 30B but associated with the first position of thesecond stretch 22 immediately downstream of the first stretch 21. Asindicated above, this condition precisely requires for stand 62 tooperatively and constructively mirror stand 60 with respect to avertical plane containing the rolling axis 100.

With reference to FIGS. 5 and 6, the second section 20 comprises firstreleasing thrust cylinders 290 positioned on the inlet side 20′ andsecond locking thrust cylinders 291 positioned on the outlet side 20″ ofthe second section 20. The second cylinders 291 exert an axial thrust onthe stands 25′, 25, 26, 27, 26′, 27′ and dummy stands 28 in a directionopposite to direction 200 in order to compact them along the rollingdirection and lock them axially. Vice versa, the first cylinders 290exert an axial thrust on the stands 25′, 25, 26, 27, 26′, 27 and dummystands 28 in a direction concordant to direction 200 in order to releasethem once they have been axially locked, in order to allow thestand-replacement operations. FIG. 8 is a view according to thesectional plane VIII-VIII in FIG. 5. FIG. 8 shows the fixed inlet stand25′ frontally, i.e. from an observation point on the rolling axis 100downstream of the first section 10. As shown in such a drawing, stand25′ is accommodated in a first lodging space 81 defined by a fixedstructure 8 which extends vertically (vertical direction 150),simultaneously defining a horizontal plane 300 on which the stand itselflies. Structure 8 further comprises a support plane 82 which extendsparallel to the support surface 300. An actuation device 130 of avertical axis drive shaft 30 is installed above the support plane 82.The vertical axis drive shaft is configured to be removably connected toa first vertical axis roller 31 of stand 25′. In this regard, there isprepared a coupling/releasing device 45 of the vertical control driveshaft 30 which is substantially installed in a second lodging space 83defined between the first space 81 and the support plane 82. Thecoupling/releasing device is configured to move the vertical drive shaft30 between a coupled position, in which the drive shaft is operativelyconnected to the first roller 31, and a released position, in which thedrive shaft instead is disconnected from the roller to allow forexample, the replacement of stand 25′.

Again with reference to FIG. 8, the actuation device 130 of drive shaft30 comprises a motor 131 and a mechanical reducer 132. The latter isinterposed above the support plane 82, between motor 131 and thevertical drive shaft 30. Preferably, motor 131 is installed so as tohave a vertical axis, i.e. so as not to emerge laterally from structure8. Thereby, the space adjacent to the sides 8′, 8″ of the structureadvantageously remains free to be exploited within the scope of thestand-replacement operation, as described below (with reference to FIGS.17 and 18).

The plan view in FIG. 7 allows to note how each stand of the sectionitself is rotated by 180° with respect to an adjacent stand, accordingto the above-described principle. In particular, it can be noted thecoupled position 125 of the vertical drive shaft related to the fixedrollers inlet stand 25′ which is rotated by 180° with respect to thecoupled position 125′ of the vertical drive shaft of a second stand 25immediately adjacent to the inlet one. The same principle applies to thecoupled position 125″ of a third stand adjacent to the second one 25,and so on. It can be noted that such a relationship is kept for all thepositions defined by the second section 20, therefore also for thesecond stretch 22 of the section itself.

It can be noted that the above-indicated technical solutions describedin the comments to FIGS. 6, 7 and 8 are valid for all the fixed stands25′, 25 installed in the second section 20 and in fact, also for theadjustable stands 26, 27, 26′, 27′ of it. For example, for each stand(fixed or adjustable), there is thus provided a corresponding actuationinstalled above the support plane 82 of structure 8 so as to keep freethe space adjacent to the sides 8′, 8″ of the structure along the wholedrive shaft thereof along the rolling axis 100.

FIGS. 9 and 10 are views related to the embodiment of a fixed stand 25according to the invention, which may be positioned in any position ofthe first stretch 21 of the second section 20 or also in a position ofthe second stretch 22. With reference to FIG. 9, stand 25 comprises abody 70 which extends between two plates 70′ and which carries therollers 31, 32, 33. The latter have a configuration which in itself isknown and they keep a fixed position, that is not adjustable withrespect to the rolling axis 100. Therefore, stand 25 always achieves thesame rolling condition, i.e. the same reduction in diameter. Overall,body 70 and the two plates 70′ are configured so as to define anoperating recess 70″ in which there are accommodated three rollingrollers 31, 32, 33, the mutual position of which in fact defines therolling axis 100.

With reference to FIG. 10, the first roller 31 has a vertical axis 101(or first axis 101) defined by a central element 71 onto which theroller itself is keyed. The central element 71 is connected on one sideto a first lateral element 71′, and on the other side to a secondlateral element 71″, which are opposite to each other with respect tothe first roller 31. More in details, the central element 71 isconnected to each of the two lateral elements 71′, 71″ through an axialconnection (e.g. axial teeth or grooved profiles) so that the threeelements 71, 71′, 71″ rotate in a synchronous manner. The first lateralelement 71′ comprises a free end 72 which may be connected to a verticaldrive shaft 30, as shown in FIG. 8, or to another functionallyequivalent actuating means.

The three elements 71, 71′, 71″ overall define a first set of elements71-71′-71″ which carries and allows the rotation of the first roller 31.In this regard, there is provided the use of a connector pin 74 arrangedlongitudinally inside the three hollow elements 71, 71′, 71″ to avoidthe removal thereof. There are also provided first supports 75 arrangedin various positions along the first axis 101 to allow the rotation ofthe elements of the set of elements 71, 71′, 71″. It is worth notingthat the axial connection between the central element 71 and the twolateral elements 71′, 71″ is removable in order to allow an easyextraction of the first roller 31 from the operating recess defined bythe body 70 of stand 25.

Similarly, for the rotation of the second roller 32, there is providedthe use of a second set of elements 76-77 defined by an axiallyconnected central element 76 (again through an axial coupling) and twolateral elements 77 rotating on second supports 75′. The second set ofelements defines a second rotation axis 102 for the second roller 32,inclined by 120° with respect to the first rotation axis 101. A thirdset of elements (indicated with numerals 76′, 77″), which isconstructively equivalent to the second set of elements 76-77, carriesthe third roller 33 thus defining a third rotation axis 103 inclined by120° with respect to the vertical axis 101 and with respect to thesecond axis 102.

Again with reference to FIG. 10, as indicated above, the first roller 31is also operatively connected to the second roller 32 and to the thirdroller 33 through drive means configured so that all the rollers areactuated by the control drive shaft 30 connected to the first set ofelements 71, 71′, 71″ related to the first roller 31. In the case inpoint illustrated, the transmission means comprise two conical drivinggears 79, 79′, each keyed onto one of the lateral elements 71′, 71″ ofthe first set of elements 71-71′-71″. A first conical driving gear 79meshes with a first driven gear 78 keyed onto the lateral element 77 ofthe second set of elements 76-77 closest to the vertical rotation axis101 of the first roller 31. Similarly, the second conical driving gear79 meshes with a second driven gear 78′ keyed onto the lateral element77′ of the third set of elements 76′-77′ closest to the verticalrotation axis 101 of the first roller 31. The transmission means aretherefore configured to achieve a synchronous rotation of the threerollers 31, 32, 33. Therefore, the conical driving gears 79, 79′ meshwith the corresponding driven gears 78, 78′ with a transmission ratioequal to 1.

With reference to FIG. 9, it can also be noted that stand 25 is providedwith a cooling system of roller 31, 32, 33 comprising an intake 174,which may be connected to an external circuit, and a cooling circuit 170comprising three end nozzles 177, each of which being configured toeject coolant close to one of the three rolling rollers 31, 32, 33. Withreference to FIG. 8, it can be noted that structure 8 of the secondsection 20 also comprises a connection device 145 forconnecting/disconnecting the above intake 174 of stand 25 to/from anexternal supply circuit. Such a connection device 145 is installed onthe side of the coupling/releasing device 45 of the vertical drive shaft30.

FIGS. 11 to 16 are related to a group of adjustable rollers stands. Inparticular, such drawings show an even bi-stand 60 which may beinstalled in the second stretch 22 of the second section 20, for examplein the configuration shown in FIGS. 1 and 3. The technical solutions forthe even stand 60 described below are to be considered valid, mutatismutandis, also for the odd stand 62. In this regard, with reference todiagrams 1-4 described above, it is underlined that the technicalsolutions described below for the first stand 26 and for the secondstand 27 of the even bi-stand 60 correspond to that provided for thesecond stand 27′ and for the first stand 26′ of the odd bi-stand 62,respectively, from a constructional viewpoint (in terms of components,definition of the motion, position of the rollers, etc.).

With reference to FIG. 11, the even bi-stand 60 comprises a first stand26 and a second stand 27 adjacent to the first stand 26. As alreadyindicated above, the first stand 26 comprises at least one drive roller,that is a roller which is motorized directly through an actuating means,preferably through a control drive shaft. According to the invention,bi-stand 60 comprises a transmission device which operatively connectssaid at least one drive roller of the first stand 26 with a drivenroller 34′ of the second stand 27 so that such a driven roller 34′ ismotorized, even though in an indirect manner, by the same actuatingmeans which motorizes the drive roller.

According to a preferred embodiment, bi-stand 60 preferably comprisesthree transmission devices, each of which operatively connects amotorized roller of one of the two stands 26 or 27, which acts as a“drive roller”, to a roller of the other stand 27 or 26 which becomes a“driven roller”. Thereby, the actuation of the six rollers of thebi-stand (three rollers for each stand) overall is achieved only throughthree control drive shafts, each of which connected to the rollers ofthe stands 26, 27 which act as “drive rollers”.

FIG. 11 is a perspective view of bi-stand 60 according to the invention.Preferably, the two stands 26, 27 which form bi-stand 60 are integratedin a single structure defined by a body 60′ which is axially closed bytwo plates 60″. Body 60′ and the plates 60″ define an operating recess61 in which there are arranged the rollers 34, 35, 36 of the first stand26 and the rollers 34′, 35′, 36′ of the second stand 27. Body 60′ alsodefines the seats for the elements which allow the rotation of therollers and the position adjustment thereof. In this regard, FIGS. 12and 13 are sectional views which allow the spatial arrangement of therollers 34, 35, 36, 34′, 35′, 36′ of the two stands 26, 27,respectively, to be noted.

With reference to FIG. 12, the first roller 34 in the first stand 26 hasa vertical rotation axis 111 (or first axis 111), while the secondroller 35 rotates about a second axis 112 inclined by 120° with respectto the first axis 111. In particular, the second roller 35 isoperatively positioned above a reference plane 105 passing through therolling axis 100 and parallel to the support surface 300. The thirdroller 36 rotates about a third axis 113 inclined by 120° with respectto the first axis 111. The third roller 36 is operatively positionedbelow said reference plane 105.

With reference to FIG. 13 and according to the principles of the presentinvention, the three rollers 34′, 35′, 36′ in the second stand 27 have aposition which is rotated by 180° with respect to the position of therollers 34, 35, 36 of the first stand 26. In this regard, it can benoted from the comparison between FIGS. 12 and 13 that also the secondroller 35′ of the second stand 27 is operatively positioned above thereference plane 105, but the rotation axis 112′ thereof is parallel tothe rotation axis 113 of the third roller 36 of the first stand 26. Thethird roller 36′ of the second stand 27 is operatively positioned belowthe reference plane 105 and the rotation axis 113′ thereof is parallelto the rotation axis 112 of the second roller 35 of the first stand 26.The rotation axis 111 of the first roller 34 of the first stand 26instead has a position which mirrors the rotation axis 111′ of the firststand 27 with respect to a vertical plane containing the rolling axis100.

With reference to FIG. 13, there is described hereinbelow the methodwith which the vertical rotation axis 111′ of the first roller 34′ ofthe second stand 27 is defined. The technical solutions hereinbelowdescribed also may be applicable to the other rollers 35′, 36′ of thesecond stand 27, as well as to the rollers 34, 35, 36 of the first stand26.

The first roller 34′ is keyed onto a central bush 134 axially connected(for example, through a cogged coupling) to a first sleeve 135 and to asecond sleeve 136. A longitudinal pin 137 is arranged inside the centralbush 134 and the sleeves 135, 136 to avoid the removal of the set ofelements 134-135-136 thus formed, according to a principle alreadydescribed above.

The second stand 27 comprises a transmission element 191 which may beconnected to an external actuating means such as e.g. a vertical axisdrive shaft. The transmission element 191 rotates with respect to thebody 60′ of stand 60 by means of suitable supports 192. It can be notedthat the transmission element 191 establishes a fixed connectionposition of the vertical drive shaft or in any case, of the actuatingmeans used.

The second stand 27 further comprises a joint 195 configured to transmitthe motion from the transmission element 191 to the set of elements134-135-136 which carry the first roller 34′. In particular, joint 195connects an end part 196 of the transmission element 191 with aconnection element 197 keyed/screwed onto a portion of the second sleeve136 of the set of elements 134-135-136. The position of the first roller34′ is adjustable through an adjusting device (described below), whilethe position of the transmission element 191 is fixed with respect tothe body 60′ of bi-stand 60. Thus, the rotation axis of the first roller34′ may take on an eccentric position with respect to the rotation axisof the transmission element 191 defined by the supports 192.

Joint 195 therefore has the specific function of keeping the set ofelements 134-135-136, and therefore the first roller 34′, connected tothe first transmission element 191 also after the variation of theposition of the rotation axis 111′ of the first roller 34′.

With reference to FIGS. 12 and 13, it can be noted that there areprovided technical solutions corresponding to those described above forthe other two rollers 35′, 36′ of the second stand 27, as well as forthe rollers 34, 35, 36 of the first stand 26. In particular, there isprovided, for all rollers, a set of support elements which defines therotation axis thereof, a rotating transmission element with respect tobody 60′ and a joint which operatively connects the transmission elementto the set of support elements according to the methods indicated above.It is reiterated again that the same technical solutions heretodescribed for the stands 26, 27 of the even bi-stand 60 are to beconsidered valid also for the odd bi-stand 62 defined above, because thelatter constructively mirrors the even bi-stand 60 with respect to avertical plane containing the rolling axis 100.

According to a preferred embodiment of the invention, the even bi-stand60 comprises a first transmission device 91 which operatively connectsthe first roller 34 of the first stand 26 to the first roller 34′ of thesecond stand 27. One embodiment of the transmission drive device 91 isshown in the sectional view in FIG. 15. In particular, the first device91 comprises a first cogged wheel 95 and a second cogged wheel 95′having parallel axes, which mutually mesh with each other. The firstcogged wheel 95 meshes a cogged portion of the transmission element 191which is connected to the set of elements 134-135-136 by means of theoscillating joint 195, which set of elements is functional to the firstroller 34′ of the second stand 27. The second cogged wheel 95′ insteadmeshes with a cogged portion of a further transmission element 191′related to the first stand 26. With reference to FIG. 12, such a furthertransmission element 191′ may be connected to a set of elements134′-135′-136′ through a corresponding joint 195′ according to the sameprinciple described above.

The rotation of the transmission element 191 is transferred through thetwo cogged wheels 95, 95′ to the other transmission element 191′, with atransmission ratio preferably equal to 1. Thereby, the two transmissionelements 191, 191′ and the corresponding set of elements 134-135-136,134′-135′-136′ rotate at the same speed. Obviously, by alternating thenumber of cogs of the elements 191 and 191′, various speeds may beobtained.

The plan view in FIG. 14 shows the transmission element 191, to which afirst vertical control drive shaft 30′ is preferably connected, as alsoshown in FIG. 16. In this regard, structure 8 of the second section 20comprises a coupling/releasing device 45′ of the first drive shaft 30′.The latter is actuated through a corresponding actuation device 130′arranged above the support plane 82 of structure 8 according to asimilar solution to that described in the comments on the fixed stand25′. Instead it can be noted, again from FIG. 16, that the transmissionelement 191′ which is functional to the first roller 34 of the firststand 26 is not connected to any external actuation due to the effect ofthe transmission device 191. According to a further aspect of thepresent invention, the even bi-stand 60 comprises a second transmissiondevice which operatively connects the second roller 35 of the firststand 26 to the third roller 36′ of the second stand 27. The evenbi-stand 60 further comprises a third transmission device whichoperatively connects the third roller 36 of the first stand 26 to thesecond roller 35′ of the second stand 27. The second transmission deviceand the third drive device have an entirely similar configuration tothat of the first device 91 described above. The use of the threetransmission devices indicated above allows the number of drive shaftsto be reduced to three, and accordingly the number of motors requiredfor moving the six rollers of the even bi-stand 60. This results in areduction of the plant manufacturing and management costs.

Preferably, the second transmission device is actuated through a seconddrive shaft 30″ which is connected to a second transmission element 198(indicated in FIGS. 11 and 12) which is functional to the third roller36 of the first stand 26. The third transmission device instead isactuated through a third drive shaft 30′″ which is connected to afurther transmission element 199 (indicated in FIG. 13) which isfunctional to the third roller 36′ of the second stand 27. The term“functional” means that one of the transmission elements 198, 199, 191,191′ mentioned is connected by means of a joint to a corresponding setof elements which supports a corresponding roller, according to theprinciples described above.

In other words, according to this aspect of the invention, the secondtransmission device and the third transmission device are actuatedthrough a corresponding inclined drive shaft 30″, 30′″ which meshes inthe corresponding transmission element 198, 199 in a position which isvery close to the support surface 300 and in any case is below thereference plane 105 indicated above. This arrangement is clearly visiblein the sectional view in FIG. 18 in which, in addition to the twoinclined drive shafts 30′, 30′″, the configuration is shown of thefoundations of the rolling mill 1 obtained for the second stretch 22 ofthe second section 20. In this regard, the inclined drive shafts 30″,30′″ are actuated through actuation means 155 in themselves known. Itcan be noted that due to the effect of the above-indicated arrangement,the foundations of the second stretch 22 have a more contained heightwith respect to the foundations of a traditional rolling section withthree-rollers stands. It can also be noted that the mutual arrangementof the three drive shafts 30′, 30″, 30′″ advantageously allows abilateral type stand-replacement plant to be made, as described below.

With reference again to FIGS. 12 and 13, bi-stand 60 comprises a firstadjusting mechanism of the position of the rollers 34, 35, 36 of thefirst stand 26 and a second adjusting mechanism of the position of therollers 34′, 35′, 36′ of the second stand 27. The two adjustingmechanisms advantageously have the same configuration. Therefore, onlythe second adjusting mechanism related to the second stand 27 ishereinbelow described for simplicity, referring to that shown in FIG.13.

The second adjusting mechanism comprises, for each of the rollers 34′,35′, 36′, a pair of lateral bushes each of which keyed onto one of thelateral sleeves which define the set of elements carrying thecorresponding roller according to the principles disclosed above. Withreference to the second roller 35′, a first lateral bush 171 and asecond lateral bush 172 are mounted on the first sleeve 135′ and on thesecond sleeve 136′, respectively, which sleeves define the set ofelements 134′, 135′, 136′ which carries the second roller 35′. Inparticular, the two lateral bushes 171, 172 are mounted on thecorresponding sleeves 136′, 135′ through suitable bearings 182. Thesecond adjusting mechanism comprises a substantially arc-shapedconnection element 173, which connects the two lateral bushes 171, 172so that the latter remain operatively connected.

Each of the two lateral bushes 171, 172 comprises a cogged portion whichmeshes a cogged portion of a corresponding lateral bush 171′, 172′mounted on a lateral sleeve related to a set of elements which carriesanother roller of the stand. Specifically, a cogged portion of the firstbush 171 meshes with a cogged portion of a corresponding lateral bush171′ mounted on the second lateral sleeve 136 of the set of elements134-135-136 which carries the first roller 34. A cogged portion of thesecond bush 172 instead meshes with a cogged portion of a furtherlateral bush 172′ mounted on a lateral sleeve 135″ of the correspondingset of elements 134″-135″-136″ which carries the third roller 36′.Through such cogged connections, the rotation and the movement in spaceof the two lateral bushes 171, 172 related to the second roller 35′causes a corresponding rotation and a corresponding movement of theother lateral bushes 171′, 172′ related to the other rollers 34′, 36′.

Again with reference to FIG. 13, the adjusting mechanism comprises anadjusting pinion 175 which may be actuated through an external device166 (indicated in FIG. 16) mounted on the support structure 8 of thesecond section 20 of the rolling mill. Preferably, the adjusting pinion175 rotates about a vertical rotation axis (parallel to the axis of thefirst roller 34′) and is operatively connected to the assembly formed bythe two lateral bushes 171, 172 and by the connection element 173 sothat the rotation of pinion 175 causes a rotation of such an assembly171-172-173 about an axis which is eccentric to the rotation axis 112′of the second roller 35′. The rotation of the assembly of elements171-172-173 causes a corresponding eccentric rotation of the set ofelements 134′-135′-136′ and accordingly, of the second roller 35′itself, which varies its position with respect to the rolling axis 100.The eccentric rotation of the set of elements 134′-135′-136′ is alsotransferred to the set of elements carrying the other rollers 34′, 36′due to the effect of the meshing between the various lateral bushes 171,172, 171′, 172′ described above. Therefore, the other rollers 34′, 36′also vary their position with respect to the rolling axis 100 incorresponding manner to the second roller 35′.

With reference again to FIG. 16, it is worth noting that the externalmechanism 166 configured for actuating the adjusting pinion 175 ispreferably installed in the second space 83 defined by structure 8. Theexternal mechanism 166 may be removably connected to the correspondingpinion 175, which emerges with respect to the body 60′ of bi-stand 60.As indicated above, the first adjusting mechanism of the first stand 26of bi-stand 60 has a configuration corresponding to that described abovefor the second adjusting mechanism, as also shown by the comparisonbetween FIGS. 12 and 13. It can be noted that the two adjustments of theradial positions of the rollers of the stands 26, 27 are independent,since they may be actuated by means of independent pinions 175 and 175′.

According to another aspect of the invention, the second section 20comprises a first platform 51 and a second platform 52 which extendlongitudinally on opposite sides 8′, 8″ of structure 8. Each of suchplatforms 51, 52 is configured to carry a replacement stand 25A, an evenreplacement bi-stand 60A or an odd replacement bi-stand 62A intended toreplace a stand or bi-stand of the second section 20. Simultaneously,the two platforms 51, 52 are also configured to carry stand 25′, 25 orbi-stand (even 60 or odd 62) of the second section 20 which is replacedby the replacement stand or bi-stand. In this regard, the second section20 comprises a shifting device 299 configured to push at least onereplacement stand/bi-stand 25A, 60A, 62A arranged on one of theplatforms (e.g. first platform 51), against a stand/bi-stand 25, 60, 62to be replaced up to the latter being completely positioned on theopposite platform (second platform 52). More in details, the shiftingdevice 299 pushes the stands along a direction 109 which issubstantially orthogonal to said rolling axis 100.

FIGS. 17 and 18 are further sectional views showing the replacementprinciple of the fixed rollers stands 25′, 25 and/or of the adjustablerollers bi-stands 60, 62. In particular, FIG. 17 shows the replacementof a fixed rollers stand 25, while FIG. 18 refers to the replacement ofan even bi-stand 60. With reference to FIG. 17, the first platform 51represents a loading platform in which the replacement stands 25A areloaded, while the second platform 52 represents an unloading platformfrom which the stands to be replaced are picked once the replacementoperation is complete. Preferably, the movement of the fixed stands 25to and from the platforms 51, 52 is performed through loading cranes orfunctionally equivalent means. This “aerial” movement is mainly allowedby the configuration given to the fixed stands whereby all the rollersare actuated through a vertical axis drive shaft. The configuration ofthe support structure 8, hence the space adjacent to the longitudinalsides 8′, 8″, is also free and the installation selections describedabove (for example, “vertical” actuations above the support plane 82 ofstructure 8) allow the aerial movement of the fixed stands and thereforeallow the reduction of the stand replacement times to just a fewminutes.

Again with reference to FIG. 17, the replacement of one fixed rollersstand 25 includes a first step in which a replacement stand 25A is keyedonto the first platform 51 (arrow 401) through a crane. The replacementstand 25A is pushed by the shifting device 299 against the stand to bereplaced 25 up to it occupying the position on the second platform 52.At this point, the stand 25 to be replaced is raised, always through acrane, and moved away from the second section 20 (arrow 402). It can benoted how the replacement principle of the stand replacement combinedwith the possibility of using a hoisting crane in fact avoids designingand manufacturing traditional replacement carriages and/or traditionalmovable tables used to replace the stands in traditional rolling millscharacterized by having horizontal drive shafts.

FIG. 18 shows how the above-described replacement principle of the fixedstands advantageously also may be used for movable stands and inparticular, for replacing the even bi-stand 60 described above. It isunderstood that the same principle may be applied to an odd bi-stand 62.Indeed, a replacement bi-stand (even 60A or odd 62A) may be easilylowered onto the first platform 51 (arrow 401), pushed by the shiftingdevice 299 against a corresponding bi-stand (even 60 or odd 62) to bereplaced positioned in the second section 20. Once the bi-stand (even 60or odd 62) to be replaced occupies the second platform 52, it may bepicked and moved away from the second section (arrow 402).

Again with reference to FIG. 18, it can be noted that in the case of abi-stand (even 60 or odd 62), the replacement principle may be applieddue to the effect of the configuration of the bi-stand itself and due tothe fact that the drive shafts 30′, 30″ inclined with respect to thevertical axis are operatively positioned below the horizontal referenceplane 105 (indicated in FIG. 13) and in position close to the supportsurface 300 of the stands 25, 26, 27 of the second section 20. In thisregard, it can be noted that the actuation means 155 of the inclineddrive shafts 30″, 30′″ are configured so as to move the same between anoperating position, in which they are operatively connected to thebi-stand, and a withdrawn position in which the drive shafts 30″, 30′″are completely below the support surface 300, thus allowing the movementof the stands along the shifting direction 109.

The rolling mill according to the invention allows the above tasks andobjects to be completely achieved. In particular, the configuration ofthe rolling mill allows the dimensions and costs of the system to becontained, and also all the problems of traditional systems generated bythe presence of intermediate heating furnaces to be eliminated. Theconfiguration provided for the second section of the rolling mill andthe structure provided for the fixed rollers stands and for theadjustable rollers stands allow the manufacturing costs of thefoundations to be minimized while simultaneously greatly reducing thecosts related to the actuations of the stands.

1. A rolling mill for tubular bodies comprising a first section forrolling on mandrel defined by a first plurality of rolling standsarranged in sequence along a rolling axis, characterized in that itcomprises a second section for extracting said mandrel and calibratingthe diameter of said tubular bodies, said second section beingdownstream of said first section, whereby said tubular bodies exitingfrom said first section directly enter said second section, said secondsection comprising a second plurality of rolling stands without mandrel,arranged in sequence along said rolling axis, wherein each stand of saidsecond section comprises three rollers, the rotation axes of which arearranged at 120° relative to one another and wherein, for each stand,said rotation axes are rotated by 180° relative to correspondingrotation axes of an adjacent stand, said position of said rotation axesbeing assessed with respect to a vertical reference direction, andwherein at least one stand of said second section comprises a motorizedroller having a vertical rotation axis.
 2. The rolling mill according toclaim 1, wherein said second section comprises at least one fixedrollers stand.
 3. The rolling mill according to claim 1, wherein saidsecond section comprises at least one adjustable rollers stand.
 4. Therolling mill according to claim 1, wherein said second section comprisesa first series of fixed rollers stands arranged in sequence along saidrolling axis starting from an inlet side of said second section, atleast one of said fixed rollers stands comprising mechanical drive meansconfigured to transmit the motion from said motorized roller havingvertical rotation axis to the other rollers of the same stand.
 5. Therolling mill according to claim 1, wherein said second section comprisesat least one dummy stand comprising at least one guide roller.
 6. Therolling mill according to claim 1, wherein each stand of said firstsection comprises three rollers, the rotation axes of which are arrangedat 120° relative to one another and wherein the rotation axes of therollers of an outlet stand of said first section are rotated by 180°with respect to the rotation axes of the rollers of an inlet stand ofsaid second section.
 7. The rolling mill according to claim 1, whereinsaid second section comprises a first stretch which defines a firstplurality of lodging positions each of which configured foraccommodating a fixed rollers stand or a dummy stand, said secondsection comprising a second stretch, downstream of said first stretch,which defines a second plurality of lodging positions each of whichconfigured for accommodating a fixed rollers stand or a dummy stand oran adjustable rollers stand.
 8. The rolling mill according to claim 3,wherein said second section comprises a group of adjustable rollersstands, said group comprising: a first stand and a second stand adjacentto said first stand, wherein said first stand comprises at least oneroller motorized by an actuating means; a transmission device whichoperatively connects said at least one roller of said first stand to atleast one roller of said second stand so that both the rollers areactuated by said actuating means.
 9. The rolling mill according to claim7, wherein said second section comprises a group of adjustable rollersstands, said group comprising: a first stand and a second stand adjacentto said first stand, wherein said first stand comprises at least oneroller motorized by an actuating means; a transmission device whichoperatively connects said at least one roller of said first stand to atleast one roller of said second stand so that both the rollers areactuated by said actuating means, and wherein said second stretch ofsaid second section defines three lodging positions and wherein saidgroup of adjustable rollers stands is configured to occupy the firstlodging position and the second lodging position downstream of saidfirst stretch.
 10. The rolling mill according to claim 7, wherein saidsecond section comprises a group of adjustable rollers stands, saidgroup comprising: a first stand and a second stand adjacent to saidfirst stand, wherein said first stand comprises at least one rollermotorized by an actuating means; a transmission device which operativelyconnects said at least one roller of said first stand to at least oneroller of said second stand so that both the rollers are actuated bysaid actuating means, and wherein said second stretch of said secondsection defines three lodging positions and wherein said group ofadjustable rollers stands is configured to occupy the second lodgingposition and the third lodging position downstream of said firststretch.
 11. The rolling mill according to claim 8, wherein said groupcomprises at least a first transmission device which operativelyconnects a first vertical axis roller of said first stand to a firstvertical axis roller of said second stand.
 12. The rolling millaccording to claim 8, wherein said first stand and said second stand ofsaid group are integrated in a single body defining an operating recessinside which the rollers of said first stand and the rollers of saidsecond stand are accommodated.
 13. The rolling mill according to claim8, wherein said first stand and said second stand of said group eachcomprise: a first roller having a vertical rotation axis; a secondroller having a rotation axis inclined by 120° with respect to saidvertical rotation axis of said first roller, said second roller beingoperatively positioned above a horizontal reference plane on which saidrolling axis lies; a third roller having a rotation axis inclined by120° with respect to said rotation axes of said first roller and of saidsecond roller, said third roller being operatively positioned below saidhorizontal reference plane, and wherein said group comprises a secondtransmission device which operatively connects said third roller of saidfirst stand to said second roller of said second stand, said thirdroller of said first stand being actuated by an actuating means.
 14. Therolling mill according to claim 13, wherein said group comprises afurther transmission device which operatively connects said secondroller of said first stand to said third roller of said second stand,said third roller of said second stand being actuated by a furtheractuating means.